ANATOMY AND I'll YS1OUXJ Y OF NEUVOIS SYSTEM. 



authors they arc spoken of as Nissl bodies, after their discoverer and 

 the man who has demonstrated their physiological worth. The gran- 

 ules are found scattered throughout the cell-body and its dendrons, but 

 not in the axis-cylinder and the adjacent area of the cell to which it is 

 attached. 



The most important relation that 

 these granules bear physiologically to the 

 cell is as follows: Under either normal 

 or abnormal activity of the nerve-cell the 

 granules undergo a change which has 

 been termed chromatolysis. It is slow 

 dissolution of the granules with diffu- 

 sion of the degenerated product into the 

 protoplasm. At first the cell swells,, 

 pushing its nucleus to one side; later the 

 cell diminishes in size, due to a loss of its 

 chromatophilic substance. 



It is in the hyaloplasm that the pig- 

 ment substance which gives to the cell its 

 particular color is deposited. 



In the discharge of nerve-energy of 

 a nerve-cell, Nissl granules are used up, 

 hence called by Marinesco, kinetoplasm, 

 a source of energy. Nissl granules dis- 

 appear or undergo chromatolysis after 

 high fever, after epileptic convulsion, or 

 after poisoning by strychnia or the toxins 

 of tetanus germs. During uraemia the 

 cells of the cerebal cortex and of the an- 

 terior horns of the spinal cord show chro- 

 matolysis. Anaemia produces similiar 

 effects. Fatigue in nerve-cells can be 

 lemonstrated by chromatolysis. 



.Nucleus. The nucleus of the nerve- 

 ill forms a small, rounded or oval mass. 



.t is characterized by its relatively large size. This nucleus is strongly 

 )lored by all the reagents, such as carmine, methylene blue, etc. 

 iround the nucleus the chromatin forms a sort of cell-wall called 



nuclear membrane. Within the nuclers is seen a small refract- 

 ing body called the nucleolus. Its chromatin is relatively great in 

 imount. 



Fig. 233. Ganglion Cell 

 from Sympathetic Ganglion 

 of Frog; Greatly Magnified, 

 and Showing Both Straight 

 and Coiled Fibers. (After 

 QUAIN.) (From Mills's 



"Animal Physiology," copy- 

 right, 1889, by D. Appleton 

 and Company.) 



